ADHD and Autism have always been present, but awareness was not the same. If you look at various historical stories and people, it is obvious that some of the people referred to had neurodivergences, they just were given different 'labels'.
The issues are the ways we treat the labels, not with having them. The names can simply help children understand the way their minds and bodies work, which may be different to others they know.
As a society, it is very hard to get diagnosis as an adult with state support. So I would encourage all who suspect their kids may have traits to investigate whilst they can. One of my DC has ADHD and Autism, with the diagnosis they can get support if/when needed.
Having learned more about them since the referral, I strongly suspect I have ADHD. However, if I get an NHS referral I get added to a list that has no movement, no-one in a position to review anyone on it. If I go private, the NHS won't recognise my diagnosis (I am in Scotland). So all future medications, if needed, have to be entirely privately self funded. And also means that a diagnosis would financially benefit the company making it, so can I truly trust they are independent?
I also strongly suspect that other family members, back to my grandparents generation, had ADHD and/or Autism. That doesn't mean they didn't have difficulties, it just wasn't understood in the same way
So when the support is not there for those who were missed as kids, living in this increasingly complex and overwhelming world, I think it is more important to ensure kids are supported when they are young and then have more options as they grow up